Various attempts have been made to provide 3 dimensional cellular scaffolds for tissue engineering applications. There are, however, many complex problems to be overcome. It is extremely difficult to provide a scaffold suitable for a range of applications because tissues and organs are comprised of a wide spectrum of different cell types and matrix structures. The functionality of the tissue or organ is determined by the type of cells present. Thus, for successful tissue growth a scaffold should be capable of supporting the growth of multiple cell types. Because of this serious problem it is not surprising that most of the tissue engineering materials developed to date have concentrated on a specific type of cell, a specific type of tissue or a specific organ. Even with this narrowed focus, however, attempts to produce 3 dimensional scaffolds of polymeric materials have not been entirely successful. One of the most serious problems is that cells will not readily attach directly to synthetic polymer surfaces. Even if initial cell adhesion were achievable there is the additional problem that adhered cells require nutrients and oxygen to ensure cell growth and proliferation. Waste metabolites excreted by the cells can also build up in the scaffold resulting in cell mortality.
Yet another serious problem is that conventional synthetic scaffolds for tissue engineering applications exude chemicals, which may alter, influence or precipitate a response from cells and foreign body and humoral immune systems. This alteration of the cell response is a particularly serious problem as the cell and tissue propagation converges to a conventional foreign body response. The foreign body response isolates the implant from the surrounding in vivo environment. Even if leachables could be eliminated the surface properties of the scaffold can alter, influence or precipitate a cell, foreign body or immune response.
There is a clear need for a tissue engineering scaffold which allows the cell propagation and expression process to be controlled, by the tissue environment, the scaffold geometry or growth factors present in the scaffold.
Yet another problem with conventional scaffolds is that insufficient surface is provided in 3 dimensions to construct a properly functioning tissue structure. Even where high surface area scaffolds are provided much of the surface is inaccessible to cells due to either nutrient or physical space issues.
There is therefore a need for a multi functional scaffold for use in tissue engineering applications, which will overcome at least some of these problems.